Fumigation or pest-control operations involving any structure, ship, or tarpaulin-covered area in which a chemical is used which does not give adequate warning of dangerous and lethal concentrations, shall require the use of Chloropicrin in conjunction with such operations. The Chloropicrin shall be applied at the rate of one ounce per 15,000 cubic feet of space or portion thereof. The Chloropicrin shall be so used as to permit penetration to all spaces under fumigation. This shall be done at least 30 minutes prior to application of the fumigant. A California licensed fumigator shall supervise all fumigation operations, and shall determine that all areas under fumigation have been so permeated by Chloropicrin as to render them humanly untenable before leaving the premises.